1. Field of the Invention
The present invention relates to a semiconductor device and method of manufacturing the same and, more particularly, to a technique for improving the reliability of a DRAM (Dynamic Random Access Memory).
2. Description of the Related Art
The micropatterning technology for semiconductor devices is remarkably developing in recent years. Especially, development of the micropatterning technology for DRAMs has been accelerated than ever. Accordingly, to ensure a sufficient capacitance of a capacitor in a limited occupation area, use of high-dielectric-constant materials for the capacitor insulating films of cell capacitors has been examined. In addition, metal electrodes which can enhance the characteristics of high-dielectric-constant materials at maximum have been developed in place of conventional silicon electrodes.
A capacitor structure having a capacitor insulating film, using a high-dielectric-constant material, and a metal electrode is proposed in, e.g., Y. Fukuzumi et al., “Linear-Supported Cylinder (LSC) Technology to Realize Ru/Ta2O5/Ru Capacitor for Future DRAMs”, IEDM 2000, p. 793. An MIM capacitor having an Ru/Ta2O5/Ru structure is proposed here.
According to the proposed structure, the adhesion between an interlayer dielectric film and a storage node electrode using ruthenium is increased by using a liner material. This structure can prevent, e.g., a wet etchant from soaking between the storage node electrode and the interlayer dielectric film. However, since liner material deposition and removal steps are necessary, the number of processes increases. Additionally, the liner material is not sufficiently resistant to oxidation. Hence, in the Ta2O5 film deposition step or high-temperature annealing step in an oxygen atmosphere, the plug material immediately under the cell capacitor may sometimes oxidizes and degrades. As a consequence, the reliability of a memory cell tends to be low.